Hey,

Normal maps aren't supposed to be used with displacement.... They are designed to be used with bump mapping. They are designed to alter the surface normals of an object, not displace it's surface, so you will only get mediocre results.

For the best results you need to convert the normal map to a Displacement map.

Your ship is looking nice BTW... the design is good, but there are some flaws. The wings are looking good, and they have nice shape, but the spikes sticking out of the sides of them just seem unpractical..... I mean what are they for? They can't be for ship to ship combat can they? As it is, they would brake off as soon as the ship entered warp drive>>>> let alone be used as a defensive/offensive weapon. (no offense) If they are there for purely aesthetic reasons then they need to have something more to them.... maybe they could carry the design of the ship a bit better.... curvy

nice work BTW..... just my thoughts.